#include<stdio.h>
#include<math.h>
int main()
{
    float s,a,b,c;
    printf("Input a,b,c:");
    scanf("%f,%f,%f",&a,&b,&c);
    if(a+b>c&&a+c>b&&b+c>a)
    {
        s=(a+b+c)/2.0;
        printf("area=%.4f\n",sqrt(s*(s-a)*(s-b)*(s-c)));
    }
    else
    {
        printf("It is not a triangle\n");
    }
    return 0;

}
